U.S. Steel Corp. operates the Minntac Taconite processing facility near the city of Mountain Iron, where it produces taconite pellets that are shipped for use at steel mills.
Minntac operates under existing air quality and industrial wastewater permits. U.S. Steel has applied for a reissued air permit so it can replace existing emissions controls in its pellet plant with cartridge filters.
Our role
The Minnesota Pollution Control Agency remains committed to protecting human health and the environment and supporting sustainable job growth in the state.
The MPCA is responsible for issuing and enforcing permits that limit emissions and discharges from Minntac’s operations to protect the environment and health of Minnesotans. Those permits reflect current state law and regulations.
The MPCA issued the facility’s existing air permit, which covers the mining area, processing facility, and tailings basin, in 2003. The permit expired in 2008 and is still current under an administrative extension. U.S. Steel submitted an application for an updated air permit in 2013. The MPCA issued a major amendment to the air permit in 2013.
The MPCA issued two wastewater permits for the facility, one for the mine site in 2003 and one for the tailings basin site in 2018.
Minntac draft air permit
The draft air permit for U.S. Steel’s Minntac Taconite plant is available for public comment through June 22, 2026. Visit the posting to review the draft document and provide feedback.
Project information
Minntac has operated as a taconite processing facility near the city of Mountain Iron since 1967. The facility consists of the Minntac plant and nearby tailings basin.
The processing plant currently uses wet scrubbers to control emissions from ore handling equipment. U.S. Steel’s permit application asks for authorization to replace those wet scrubbers with dry cartridge filters to reduce particulate matter emissions.
Minntac has already completed all other construction associated with minor amendments and notifications in the permit application.
The draft permit includes requirements for U.S. Steel to:
- complete a National Ambient Air Quality Standards (NAAQS) compliance demonstration within the next permit term
- update its performance test schedule for emissions units subject to the taconite maximum achievable control technology (MACT) standard
- comply with updated taconite MACT standard requirements
- incorporate regional haze federal implementation plan limits
- ensure the proper operation of control equipment
Next steps and timeline
The draft air permit is available for public comment from May 15-June 22, 2026. Submit comments here.